The next government could struggle to fund public services because of the biggest debt challenge since the 1950s, according to a respected thinktank.
Whichever party wins the next election may be unable to fund key services if politicians are not transparent about the trade-offs they face, the Institute for Fiscal Studies (IFS) says in a new report.
Higher borrowing costs, as a result of increased interest rates, as well as low economic growth and both the Conservatives and Labour committing to reduce debt, leave the next government with little financial flexibility, the IFS adds.
It could be one of the most difficult parliaments for tax and spending since the 1950s, according to the report.
It says: "These challenges - unlike a conflict, pandemic or financial crisis - are entirely predictable.
"None can be meaningfully confronted by a government that wilfully ignores reality and the need to choose between difficult competing options.
"As tempting as it may be to engage in 'cakeism' - to seek to have the government's fiscal cake and eat it - any party serious about governing after the election should resist the urge. The electorate surely deserves better than that."
The government will have to achieve something that hasn't been done in 20 years - tax takes and state revenue streams will have to rise to become greater than government outgoings.
This is more difficult at present with the current high debt interest payments and low growth forecasts.
Achieving debt reduction goals by raising taxes may also be politically unpalatable as the UK tax burden, the amount of taxes paid as a percentage of national income, is at a high not seen since the Second World War.
Potential budget cuts will be difficult, too, the IFS says - as living standards have been in a period of "record-long stagnation" and public services are "visibly struggling, and performing less well than they were back in 2010".
But public services, except health, are to have an effective budget cut as funding isn't being "sufficiently topped up", the IFS said at the time of the autumn statement.
The thinktank says political parties need to "be honest with the public about the tough trade-offs they will inevitably have to make on tax and spending".
"If they are promising tax cuts, let's hear where the spending cuts will fall. If they are going to raise, or even protect, spending, they should tell us where taxes will rise," IFS director Paul Johnson said.
"Or parties might think that further increases in government debt are justified: in which case they should make the argument for why debt should be rising."